This invention relates to the field of techniques for mounting and making connections to piezoelectric crystals.
Thin crystal blanks, formed by slicing an artificially grown crystal having the desired electrical characteristics, have typically been mounted at the edges in order to provide a large surface area which is free to vibrate. Since techniques have now been developed for putting relatively complex circuitry on a single crystal, edge-mounting has proven to be less desirable. Crystal mountings are known which support the crystal on a conductive support usually at the center, with the second contact made directly opposite by a second support post or by a soldered wire.
Simple opposing supports are, of course, not possible for more complex circuitry, since the requisite multiple contacts must be separated by as much distance as possible on a small crystal. This is mainly because separate portions of the circuitry may well be operating at different frequencies and interference must therefore be minimized.
In the case of multiple contacts, a problem arises when wire bonds are made to portions of the crystal which are unsupported; i.e., not opposite the support member, and the rate of crystal breakage therefore becomes excessively high. These areas, however, cannot be supported during operation of the crystal in an electronic circuit, since the ensuing amount of acoustic damping would be unacceptable.